(CNN) -- The American Civil Liberties Union is pushing for a quick legal decision, hoping to save a high school prom that was allegedly canceled because two lesbians wanted to attend it together.

The rights group filed a motion for a preliminary injunction against a Mississippi school district and high school in federal court Tuesday over the April 2 prom.

The case will be argued before a federal judge in Mississippi on March 22, the ACLU said.

The showdown stems from a complaint by 18-year-old Constance McMillen, who said she was told not to bring her girlfriend to the prom or wear a tuxedo.

The prom was canceled after the ACLU demanded that McMillen's high school change its policy.

"I never thought the school would try to cancel the prom and hurt everyone just to keep me and my girlfriend from going together," McMillen said in an ACLU news release. "A lot of people have made really generous offers to pay for a prom somewhere else, which I really appreciate. But all I've ever wanted was to be able to just go to my own school's prom with my girlfriend."

The motion filed Tuesday is part of a lawsuit that the ACLU has filed against the Itawamba County School District and Itawamba Agricultural High School.

At the center of the lawsuit is a memorandum from the school to students, dated February 5, which says that prom dates must be of the opposite sex.

Also, when McMillen expressed a desire to wear a tuxedo to the prom, the district superintendent told her only male students were allowed to wear them, according to court documents.

Superintendent Teresa McNeece also told McMillen that she and her girlfriend could be ejected from the prom if other students complained about their presence, according to the documents.

School district officials could not be reached for comment. But the county's board of education said in a statement last week that "Due to the distractions to the educational process caused by recent events, the Itawamba County School District has decided to not host a prom at Itawamba Agricultural High School this year."

The ACLU aims to change that.

"We are determined to get the prom back on the calendar and open to all students," said ACLU lawyer Christine Sun. "What this case comes down to is the school taking the extraordinary measure of canceling the prom, rather than live up to its legal obligation to fairly treat all students who want to come to it."